A frequent approach to water scarcity management in urban distribution systems is based on intermittent supply. The analysis of the transient occurring during the filling process of the network distribution is particularly complex thus some simplifying assumptions have to be made. The actual numerical models consider the air pressure at the water front face always atmospheric, the water column fronts coincident with pipeline cross-sections and the steady-state formulae used to calculate frictional resistance. Although the first two hypotheses can be considered satisfied, it has been demonstrated [1] that the classical steady friction model produces an underestimation of the energy dissipation. Due to the extreme complexity of such problem, the numerical studies of the transient flow arising in network pipes neglect the unsteady terms of the friction factor. In the present analysis the numerical method based on the Method of Characteristics, used by [2], has been developed taking into account the frictional dissipation in unsteady flow conditions. The numerical model is firstly tested against laboratory data collected and then the modified dynamic model was applied to a network in Palermo (Italy). The effect of the unsteady friction model during the filling process is explored.
A numerical unsteady friction model for the transient flow arising during the filling process of intermittent water distribution systems
DE MARCHIS, MAURO;FRENI, GABRIELE;
2011-01-01
Abstract
A frequent approach to water scarcity management in urban distribution systems is based on intermittent supply. The analysis of the transient occurring during the filling process of the network distribution is particularly complex thus some simplifying assumptions have to be made. The actual numerical models consider the air pressure at the water front face always atmospheric, the water column fronts coincident with pipeline cross-sections and the steady-state formulae used to calculate frictional resistance. Although the first two hypotheses can be considered satisfied, it has been demonstrated [1] that the classical steady friction model produces an underestimation of the energy dissipation. Due to the extreme complexity of such problem, the numerical studies of the transient flow arising in network pipes neglect the unsteady terms of the friction factor. In the present analysis the numerical method based on the Method of Characteristics, used by [2], has been developed taking into account the frictional dissipation in unsteady flow conditions. The numerical model is firstly tested against laboratory data collected and then the modified dynamic model was applied to a network in Palermo (Italy). The effect of the unsteady friction model during the filling process is explored.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
